CI: Update used node version to 16 (bytecodealliance#2303)

Since building the extension now depends on node >=16 (see bytecodealliance#2292),
build_wamr_vscode_ext.yml will fail on the next release without this change.

.github/workflows/build_wamr_vscode_ext.yml

@@ -20,10 +20,10 @@ jobs:
     steps:
       - uses: actions/checkout@v3
 
-      - name: Use Node.js 14.x
+      - name: Use Node.js 16.x
         uses: actions/setup-node@v3
         with:
-          node-version: 14.x
+          node-version: 16.x
 
       - name: set vscode extension to correct version
         run: |